The present invention relates, in general, to a mold assembly for encapsulating semiconductor devices, and more particularly, to a mold assembly having positioning means for positioning the semiconductor device within a cavity of the mold.
Mold assemblies for encapsulating semiconductor devices to form semiconductor packages are well known. There are many different semiconductor packages to meet different user requirements or to accommodate the many different semiconductor devices. Some semiconductor packages completely encapsulate the semiconductor device and the heatsink on which it is mounted. Other semiconductor packages leave exposed at least one surface of a heatsink upon which the semiconductor device is mounted. This exposed surface of the heatsink can later be mounted or mated to a heat exchanger to facilitate removal of heat from the semiconductor device. Many of the semiconductor packages have become standardized by JEDEC and are known by designations such as TO-218, TO-220, etc. A problem arises when the semiconductor packages that have interface pins extending from only one side of the package need to have the heatsink entirely encapsulated. In the past such heatsinks have been held in position within the cavity of a mold assembly by straight pins extending from the top and bottom of the mold assembly itself. These straight pins made physical contact with the top and bottom sides of the heatsink holding the heatsink in a position away from the walls of the cavity. Since the heatsink was positioned away from the walls, encapsulating material could completely surround the heatsink except for the small area where the pins made contact to the heatsink.
After the encapsulating procedure was completed, foreign material such as encapsulating material bleed or mold release compound had to be cleaned from the holes left in the encapsulating material by the straight pins, and then these holes had to be filled with a backfill material such as an epoxy or silicone. This was a time consuming procedure and was very labor intensive.
Accordingly, it is an object of the present invention to provide a mold assembly and method of using the same that entirely encapsulates one side of a heatsink while providing point contact positioning means on the opposite side of the heatsink.
Another object of the present invention is to provide a tapered configuration to the positioning means.
Yet another object of the present invention is to provide means within a mold cavity for holding a heatsink in a desired position wherein direct contact is not made to one side of the heatsink.